Conventionally, as this sort of semiconductor capacitance type sensor, for example, semiconductor mechanical amount sensors such as acceleration sensors and angular velocity sensors have been proposed (in, for example, JP-A-2004-271312 corresponding to US Patent Application Publication No. 2004-0173913). These semiconductor capacitance type sensors correspond to such sensors equipped with sensor chips having movable electrodes and fixed electrodes and functioning as capacitance changing portions. Then, when mechanical amounts such as acceleration and angular velocities are applied to such sensor chips, distances between the movable electrodes and the fixed electrodes are changed, so that capacitance changes may be conducted.
Then, while these sensor chips are assembled with circuit chips, the capacitance changes of these sensor chips are converted into voltage changes, namely, voltage signals by CV converting circuits (namely, capacitance-to-voltage converting circuits) provided in the circuit chips. Thereafter, the voltage signals are outputted as sensor signals, so that the applied mechanical amounts are measured.
Such semiconductor capacitance type sensors have been manufactured as follows: That is, while sensor chips and circuit chips are manufactured respectively by performing semiconductor process operations, characteristics of the sensor chips are tested under condition of a single sensor chip, and thereafter, such sensor chips which are judged as good products are assembled with the circuit chips, and thus, these sensor chips and circuit chips are electrically connected to each other.
In general, characteristic testing operations as to sensor chips are carried out in such a way that capacitance changes in capacitance changing portions are checked by employing such testers as an LCR meter. While probes of the testers are attached to pads of the sensor chips, capacitances of the capacitance changing portions are converted into voltages within the testers under this condition in order to test the sensor characteristics.
Also, as methods for measuring capacitances of semiconductor capacitance type sensors other than the above-described capacitance measuring methods, conventionally, another method for measuring capacitance values has been proposed (in JP-A-2000-321300). That is, in this capacitance value measuring method, while a plurality of sensor chips are employed, capacitance values of these sensor chips are measured, and asymptotes are calculated which represent a relationship between the measured capacitance values and distances defined between the capacitances and the electrodes, so that the capacitance values are acquired.
In the above-described method for testing the sensor characteristics under the single sensor chip condition by utilizing the tester, stray capacitances produced at the probe portion of the tester which are attached to the pads provided in the sensor chip and stray capacitances of these pads are large, for example, approximately 1 pF to 100 pF, with respect to very small capacitance values (for example, approximately 1 pF) of the capacitance changing portions.
As a result, the conventional characteristic testing methods have the following problems. That is, errors contained in the capacitance values acquired by the testing operations become large with respect to the capacitance values of the sensor chips under such a condition that these sensor chips are electrically connected to the circuit chips, namely under packaging condition of the sensor chips, so that the high-precision capacitance value measuring operations can be hardly carried out.
Also, in the measuring method, although the capacitance values are predicted by employing the asymptotes, the adverse influence caused by the stray capacitance can be hardly avoided. Thus, there are some possibilities that the errors contained in the capacitance values measured by this method become larger with respect to the capacitance values under the packaging condition.
Also, another characteristic testing method may be conceived. That is, sensor chips are assembled with circuit chips, which are cut out from a wafer, so as to be brought into packaging members. Thereafter, a characteristic as to each of these packaging members under packaging condition may be tested. However, in this conceivable method, a large number of these packaging members must be picked up one by one, and these picked packaging members must be separately mounted on a testing apparatus, resulting in cumbersome handling operations.
Furthermore, another testing method may be conceived. That is, a wafer where structural members which constitute sensor chips have been formed is employed before the sensor chips are cut out, and then, an electric testing operation is carried out under present condition of this wafer. However, in this conceivable method, since probes of a tester are attached to pads of the wafer, materials of these pads are scooped out. Thus, there are some risks that the scooped materials are adhered as alien substances to capacitance changing portions.
Therefore, it is required to provide a packaging condition with a superior handling characteristic when a characteristic testing operation is carried out, and furthermore, while avoiding that alien substances are adhered onto the capacitance changing portions, the characteristic testing operations of the sensor chips can be carried out.